Introduction to Wireless

09/20/2001

Today there is likely no hotter area of development than wireless networking. Wireless 802.11 networks have been in the news quite a lot recently, both from the perspective of their growing popularity and in terms of the security vulnerabilities that have been recently discovered in the Wired Equivalent Privacy (WEP) security standard that is supposed to ensure the security of data that flows over these networks.

The low cost of wireless hubs and wireless cards has brought this exciting new technology into the realm of affordability for almost anyone. Wireless networking hubs, called "access points" can be purchased for as little as USD$300, and with manufacturer rebates, wireless PC cards for laptops and handhelds are under $100 from most online discounters.

So, with all this activity, it seems a perfect area to explore for the Linux-centric enterprise to enable your users to liberate themselves from the shackles of CAT5 cables and get a breath of fresh air. But before you dive in, make sure there's some water in the pool!

What wireless networking is, and isn't

Countless articles have been written to explain the inner workings of the 802.11b wireless networking standards, including some excellent pieces elsewhere on the O'Reilly Network that detail how to experiment with long-distance wireless networking using this technology. But it's a good idea to look at what wireless networking can do with a set of glasses that remove the hype.

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If you believed the marketing claims of the 802.11 wireless industry, you would think your whole business can just hop on a set of wireless hubs, and that all you have to do is put a wireless card into your laptop or handheld and you're off to the races and will never need wires again. Unfortunately, this just isn't the case. Wireless networks require a lot of planning and infrastructure support to make them useful and even more attention to security than their wired counterparts to make them "safe" in a business (or even home) environment.

Wireless networks are not as secure as wired networks

One of the scariest revelations of the past couple of months is that the so-called Wired Equivalent Privacy (WEP) protocol built into every 802.11 network card and access point is fundamentally insecure and sensitive data sent over wireless networks using WEP can be easily broken.

What this means from a practical perspective is that unless you take some very serious counter measures (which we'll cover in the next article), 802.11 networks should not be used in situations where critical data (such as passwords, patient files, or monetary transactions) will be sent over the airwaves. Unlike wired networks, the data on wireless networks is, quite literally, broadcast for all the world to hear. There are even sites on the Internet dedicated to "mapping" 802.11 networks so that people can walk the streets with laptops and find open networks that can be accessed "for free."

I would like to point out that even though people are accessing these unprotected networks, it's still criminal trespassing and theft of services. I would strongly advise against it -- law enforcement these days has a very little sense of humor and is more likely to put people in jail than to let them off with a stern warning.

Wireless networks are not Ethernet switches

Wireless networking systems are a lot like the old party-line phone systems that existed in the early part of the 20th century. 802.11b implements a shared Ethernet-like system where everyone competes for a chance to use the available resources (bandwidth). In party-line phone systems, if someone else was on the line, you would have to wait until the other party was done before you could place your call. Unfortunately, because early telephone systems were a shared medium, other people could also listen in on your private conversations.

Wireless networks work in the same way; all of the wireless users (called "stations" in 802.11 parlance) share a slice of radio frequency spectrum in the 2.4 GHz range. They each talk to a wireless base station or "access point" that acts as a communications controller and router. The access point routes packets from individual stations to each other, or to a wired network that is connected to the access point if the packets are destined for some other network, such as your corporate backbone or the Internet. Unlike modern wired networks that are built on top of Ethernet switches, it's possible for a single station to completely monopolize the available network capacity.

How fast is that wireless network, really?

The 802.11b standard gives stations on a wireless network a theoretical 11 megabits per second of bandwidth to play with. Well, at least this is true for devices that are in very close proximity to the wireless access point/hub. However, the farther you get away from the hub, the more your access speed to that hub goes down.

Fortunately, the 802.11 specification handles this pretty well, and access speeds decline gracefully and are continuously and dynamically re-evaluated so your speeds may go up and down depending on distance and other conditions. What this means from a practical perspective is that wireless networks are not (yet) the best thing to run streaming audio and video on if you are expecting to let a lot of users share an access point.

Where to use wireless

Well, now that I've probably made you fear that 1) your passwords will be cracked, 2) random people could be accessing your network from a nearby park bench, and 3) that users downloading MP3s can eat up all your wireless bandwidth, where exactly can or should you use wireless networks?

Wireless networks are a great mechanism to allow laptop and handheld users to get access to a network without having to dedicate network hardware (switch ports) to them.

Wireless networking also makes great sense in common areas such as cafeterias, auditoriums, and conference rooms where people often need to take notes, access web material, or have other other types of online needs, and where it's just plain impractical to provide enough hard-wired connections to meet everyone's needs.

Wireless networks are excellent for giving access from kiosk-type systems for public Internet connections, or even in lobby areas where you want visitors to be able to look at your corporate web site or to browse other information.

With appropriate security measures in place, you can even use wireless networks for sensitive applications. We'll cover that aspect of using 802.11 in the next article in this series.

In the next article

The next articles in Linux in the Enterprise will delve into strategies you can use to make your wireless networks more secure -- from the laptop/handheld side of things to your network servers -- and will include discussion of how to deploy and manage access points and wireless network cards in the Linux environment.

David HM Spector
is President & CEO of Really Fast Systems, LLC, an
infrastructure consulting and product development company based in New York